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Bcl-2, via its BH4 domain, blocks apoptotic signaling mediated by mitochondrial Ras
Gerald V Denis1, Qiang Yu, Peihong Ma
1Cancer Research Center and Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Abstract:
Bcl-2 protects cells against Ras-mediated apoptosis; this protection coincides with its binding to Ras. However, the protection mechanism has remained enigmatic. Here, we demonstrate that, upon apoptotic stimulation, newly synthesized Bcl-2 redistributes to mitochondria, interacts there with activated Ras, and blocks Ras-mediated apoptotic signaling. We also show, by employing bcl-2 mutants, that the BH4 domain of Bcl-2 binds to Ras and regulates its anti-apoptotic activity. Experiments with a C-terminal-truncated Ras or a farnesyltransferase inhibitor demonstrate that the CAAX motif of Ras is essential for apoptotic signaling and Bcl-2 association. The results indicate a potential mechanism by which Bcl-2 protects cells against Ras-mediated apoptotic signaling.
Insights
The anti-apoptotic protein Bcl-2 binds to Ras at the mitochondria, blocking Ras-mediated apoptosis. This interaction, mediated by Bcl-2's BH4 domain and Ras's CAAX motif, reveals a novel cell survival mechanism.
Area of Science:
- Cell biology
- Molecular oncology
- Apoptosis research
Background:
- Bcl-2 protein is known to protect cells from apoptosis induced by Ras.
- The precise mechanism by which Bcl-2 confers this protection, despite binding to Ras, remains unclear.
- Understanding this interaction is crucial for developing targeted cancer therapies.
Purpose of the Study:
- To elucidate the mechanism of Bcl-2-mediated protection against Ras-induced apoptosis.
- To identify the specific domains of Bcl-2 and Ras involved in their interaction and functional outcome.
- To explore the role of Ras post-translational modification in this protective pathway.
Main Methods:
- Utilized Bcl-2 mutants to map functional domains involved in Ras interaction.
- Employed C-terminal-truncated Ras and farnesyltransferase inhibitors to probe the role of the CAAX motif.
- Investigated the subcellular localization and interaction of Bcl-2 and Ras upon apoptotic stimulation using biochemical and imaging techniques.
Main Results:
- Newly synthesized Bcl-2 translocates to mitochondria during apoptotic stimulation.
- Bcl-2 directly interacts with activated Ras at the mitochondria, inhibiting Ras-mediated apoptosis.
- The BH4 domain of Bcl-2 is essential for binding to Ras and mediating anti-apoptotic activity.
- The CAAX motif of Ras is critical for both Ras-mediated apoptotic signaling and its interaction with Bcl-2.
Conclusions:
- Bcl-2 protects against Ras-induced apoptosis by directly binding to activated Ras at the mitochondria.
- This interaction is regulated by Bcl-2's BH4 domain and requires the CAAX motif of Ras.
- The findings reveal a novel molecular mechanism for Bcl-2-mediated cell survival in the context of oncogenic Ras signaling.